1985 380 SL mushy brakes

[tshort]

My son's 1985 380SL brakes are soft and mushy. So we replaced the front calipers with new rebuilt ATE's. new front pads, new rear pads and bleed the lines. No help so we replaced the Master brake cylinder ( bought at Kragens) and the vacuum hose line going to the booster ( bought at Mercedes). Still soft and no brake fluid leaks. Last two parts left that I know little about are brake booster and convergence valve. Any thoughts on how to test? Thanks in advance

[Larry Delor]

Replacing the flexible brake lines, would be the next thing that I would do - they can degenerate on the inside, and look fine on the outside.
http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=22Q14UFJL27C1E7OTN&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1985&product=N7000-16092&application=000243572

[tshort]

Larry, I replaced 1 of the 2 front since it broke during the replacement. The other 3 have not been done but I don't believe that is the issue since the brake fluid streams out on bleeding very well. Do you know how to check the booster or convergence valve ( prior to ABS) it is suppose to balance pressure. The master brake cylinder sends a front and back line to the convergence valve and then from their it sends out the pressure to each brake. Thanks Thomas

[RickM]

Originally Posted by tshort

Larry, I replaced 1 of the 2 front since it broke during the replacement. The other 3 have not been done but I don't believe that is the issue since the brake fluid streams out on bleeding very well.

Thomas, I think what Larry is saying is that the interior portion of the lines deteriorate with time. It is a common item to replace as the lines stretch with time, especially 22+ years. Stretch = mushy.

[TX76513]

Larry is right on - have somebody step on and hold the brake down while you look at the lines - look for "ballooning"

[ctaylor738]

Are you using a pressure bleeder? Highly recommended.

If not, be sure that both chambers of the reservoir are full before you start pumping and are not dropping and allowing air into the system. One of the chambers takes a few minutes to fill and if you start pumping right after adding fluid, you get air in the lines.

Also, at the bleeders, be sure to use a clear hose and a good light to be sure that you're not getting tiny bubbles in the fluid.

And you did go RR, LR, RF, LF, didn't you?

[tshort]

Appreciate the advice since I did rears first but not the specific order. I will also use my professional bleeder which has the clear tubes after I replace the other 3 lines. Thanks To everyone. Thomas